This invention relates to data transfer in a computer system. In particular, the technique disclosed herein relates to improving the rate of data transfer via a switch fabric.
There have been proposed systems which support remote I/O by connecting a host computer and an I/O device through a switch fabric (see, for example, an article written by Paul Millard et al., titled “PCI Express Switching and Remote I/O in the Data Center”, published on February 2005 through xyratex, ASI-SIG, retrieved on Aug. 3, 2006 at http://www.asi-sig.org/education/whitepapers/Remote_IO_WhitePapaer.pdf. and an article written by Stephen Christo et al., titled “Application Examples Enabling Virtual IO and Storage”, published on Jun. 15, 2006 through xyratex, ASI-SIG, retrieved on Aug. 3, 2006 at http://www.asi-sig.org/education/presentations/3_ASI_Apps_Examples_StarGen.pdf). Such systems (hereinafter referred to as remote I/O systems) consolidate resources and provide flexible I/O, thereby making it possible to cut the investment cost.
Direct memory access (DMA) transfer is a well known method of data transfer in computer systems (see, for example, JP 2002-215563 A, JP 08-95899 A, and JP 08-30544 A). With DMA transfer, where data transfer is executed between a device and a memory without the intermediation of a CPU, data can be transferred at high speed.